Commuter ferry service to Yonkers received a $300,000 boost from the Empire State Development Corp. last month.

Without the money, the New York Water Taxi service between Lower Manhattan and Yonkers likely would have ended in July. The grant has allowed Water Taxi and the City of Yonkers to not only keep the ferry service going, but also to launch an advertising campaign and add a new stop: W. 39th St.

The enhanced ferry route went into effect Aug. 3 and includes the original stops of Pier 11 near Wall St., the World Financial Center and Yonkers in addition to W. 39th St.

The $300,000 grant will support the ferries for another three months, which will hopefully be enough time for the marketing to produce results, said David Simpson, a spokesperson for Yonkers Mayor Phil Amicone.

In particular, Simpson is banking on the new stop in Midtown to make the service more attractive and increase ridership.

“I know a lot more people living in lower Westchester who work in Midtown than in the Financial District,” Simpson said. “It’s just where most of the larger firms are now.”

The Yonkers ferry once extended up to Haverstraw, but Water Taxi discontinued that service May 1 because few people used it. The ferry, which began in 2007, was originally subsidized by the Lower Manhattan Development Corp., an E.S.D.C. subsidiary.